By 1926, the former GER B12 class locomotives were no longer able to cope with the heaviest express passenger trains on the Great Eastern Main Line between London and Cambridge, Ipswich and Norwich.

[3] After several unsuccessful attempts by Doncaster Works to satisfy Gresley's specification, the contract for the detailed design and building of the class was given to the North British Locomotive Company in 1927.

Due to weight restrictions it proved to be impossible for all three cylinders to drive the middle coupled axle.

The design continued to prove problematic and the LNER eventually cancelled a penalty clause in the original contract.

Five further orders were placed with Darlington Works between December 1928 and March 1935 for a further fifty-two locomotives to be delivered between August 1930 and June 1936.

A final batch of eleven were ordered from Robert Stephenson and Company in February 1936 (works nos.

The final Darlington batch introduced in 1936, and those built by Robert Stephenson and Company had 4,200-imperial-gallon (19,000 L; 5,000 US gal), 7.5-long-ton (7.6 t) tenders and were intended for use in the North Eastern area of the LNER: these were designated B17/4.

[7] Between 1943 and 1957 most of the surviving members of the class were rebuilt with a LNER 100A boiler with increased pressure and were designated B17/6.

In October 2020 the project relocated to CTL Seal's premises in Sheffield, with the chassis moving from Llangollen and the tenders from the Mid-Norfolk Railway.

[16] The North British Locomotive Preservation Group were engaged in a project to build a non-operational LNER Class B17 4-6-0 replica, named after a football club, 61662 Manchester United.